Idea for Armor DR for non-shifters

I've been trying to think of a way to improve sword and board characters that wouldn't improve shifters and was curious if it is possible to add some small DR to armor and shields for non-shifters, with a fullplate and towershield char getting the highest benefit, as they should technically be tankiest. I've always thought it was silly that wearing fullplate and a towershield wouldn't give you more protection than being dextrous when you get hit. Could code the shield DR to be removed when flanked too, assuming that kind of thing isn't hard   I have no idea how feasable any of this would be, but it might help traditional tanks tank without having to cheese.